As a process for coloring a powdery polyurethane resin, there has been known a process, in which a pigment is added and mixed into this resin.
A process, in which a plasticizer is added and mixed together with a pigment into a powdery polyurethane resin, has also been introduced (see Patent Document 1).
Further, a process, in which a pigment is added and mixed into a powdery polyurethane resin, and a plasticizer is then added thereto and further mixed, has been introduced (see Patent Document 2).
Patent Document 1: Japanese Patent Application Laid-Open No. 2004-67954
Patent Document 2: Japanese Patent Application Laid-Open No. 2005-154451